For its first 110 years, the Cosmos Club did not permit women members, and forbade female guests to enter by the front door or to enter rooms reserved for members. In 1987, the Washington, D.C., Human Rights Office ruled that there was probable cause to believe that the club's men-only policy violated the city's anti-discrimination law. The Office was ready to order public hearings on the case, which could have resulted in the loss of all city licenses and permits if the all-male policy had continued, but the Cosmos Club then voted on June 19, 1988, to accept women as members.[1]

In 1990, the Cosmos Club began publication of Cosmos: A Journal of Emerging Issues as an annual publication of original essays by its members.[2][3]

Election to membership in the Cosmos Club honors persons deemed to have "done meritorious original work in science, literature, or the arts, or... recognized as distinguished in a learned profession or in public service".[6]